Vehicle interior panels typically include a decorative aspect, providing the passenger cabin of a vehicle with a desired aesthetic. Combinations of different types of materials, textures, shapes, tactile features, and visual features can be used with such panels to provide a particular passenger cabin with any of a variety of different ambiences, from luxurious to utilitarian. Visible stitching, whether actual sewn stitching or simulated stitching, is sometimes used as an element in vehicle interiors to indicate luxury. Stitching features are reminiscent of hand-crafted materials such as custom leather upholstery, considered luxurious in a day and age of automated high-speed manufacturing. Where sewn stitching is employed, the associated needle holes can sometimes lead to other visual defects, however, such as underlying materials showing through the needle holes.
U.S. Pat. No. 6,401,643 to Iida discloses a sewn cover assembly of a type that is to undergo a foaming process involving injection and curing of a liquid foaming material therein. The cover assembly is formed by sewing together plural cover elements via two different sewing threads. One of the two threads is larger in thickness than the other and is intended to prevent leakage of the liquid foaming material where the cover elements are sewn together.